The present invention relates generally to flat panel antenna arrays for generating multiple, simultaneous, beams for the transmission and reception of directional microwave communications.
The rapid expansion of the delivery of wireless services for telephony, messaging and internet access is generating the need for more advanced and cost effective antenna solutions than are currently available. One such solution is the multiple beam base station antenna used in point to multi-point delivery systems. This single antenna acts like a number of antennas superimposed on top of one another to deliver full aperture gain beams to adjacent azimuth sectors. Multiple beam antennas increase the channel capacity of a system without the need to install additional antennas by allowing multiple transceivers to be connected to a single base station antenna and thereby communicate with multiple subscribers, each subscriber within a sector covered by one of the beams generated by the antenna. In addition to being able to increase system capacity, these multi-beam antennas can also be integral parts of xe2x80x9csmart antennaxe2x80x9d systems that can also increase the performance of wireless delivery systems in various ways such as the following: Smart antenna systems may xe2x80x98followxe2x80x99 mobile subscribers electronically; multiple sectors may be covered with a single transceiver; signal integrity may be enhanced through beam diversity; and any given beam may be dynamically shaped to enhance interference rejection. Advantages of smart antenna systems are addressed by Richard H. Roy, xe2x80x9cApplication of Smart Antenna Technology in Wireless Communication Systemsxe2x80x9d, White Paper produced at ArrayComm, Inc., 3141 Zanker Road, San Jose, Calif. 95134, which paper is incorporated herein by reference.
In accordance with preferred embodiments of the invention, there is provided an antenna array. The antenna array has a multi-beam forming network disposed on a circuit board in plane referred to as a network board plane. The antenna array also has a plurality of radiator boards, each radiator board disposed in one of at least one radiator board plane in such a way that each radiator board plane is perpendicular to the network board plane. Several radiator elements are disposed on each radiator board and coupled to the multi beam forming network so that the plurality of radiator elements create at least one beam directed in a specified direction.
While antenna beams are described herein in terms of transmission and radiation of electromagnetic energy, it is to be understood that such description applies in equal measure to the reception of such radiation.
In accordance with further embodiments of the invention, the multi-beam forming network may be a time delay structure, or, more particularly, a Rotman lens. Beam ports of the Rotman lens may be coupled pairwise to individual input connectors. The antenna may also have an array port circuit for coupling energy to the radiator boards, and at least one attenuator in the array port circuit.
In accordance with yet further embodiments of the invention, each radiator board may also include an elevation feed network, and each radiator element may be a dipole element. The antenna array may also have a first ground sheet with a plurality of slots, a radiator board extending through each slot of the first ground sheet. The antenna array may also have a second ground sheet with slots, a radiator board extending through each slot of the second ground sheet. The ground sheets may interlock with notches in the radiator boards so as to create a plurality of effective slots narrower than the characteristic width of the radiator boards. Additionally, a plurality of cross braces may be provided, one cross brace disposed across each row of radiator boards.
A radome having no mechanical contact with either the network board or the radiator boards may be provided, in accordance with a further embodiment of the invention, for shielding the multi-beam forming network and radiator boards from environmental effects.